Medication delivery pens have been developed to facilitate the administration of medication, particularly the self-administration of medication. Such medication delivery pens may be referred to herein as an injector device, a self-injection drug delivery device, a pen style drug delivery device, a pen, and other variations thereof. Such pens may be disposable, containing a single dose of a drug, or reusable, containing a single dose or more of a drug. The pen typically includes a vial or drug cartridge containing a drug and a dose setting mechanism which allows both for selecting a dose of medication to be delivered by the pen and for urging a plunger of the vial in a distal direction for a distance corresponding to the selected dose, thereby allowing the dose to be administered.
Certain drugs or medicaments (those terms being used interchangeably herein) are preferably provided in powder or dry form (sometimes referred to a lyophilized form), and require reconstitution prior to administration. Lyophilized drugs, for example, typically are supplied in a freeze-dried form that needs to be mixed with a diluent to reconstitute the substance into a form that is suitable for injection. Medicaments may also be provided in other powder form that require reconstitution.
Prior art devices have been developed that provide the diluent and lyophilized substance in separate chambers of a common container. Such devices permit manual reconstitution of the drug prior to administration. U.S. Pat. No. 4,874,381 to Vetter and U.S. Pat. No. 4,968,299 to Ahlstrand et al. are examples of manually activated devices which require a user to physically move one or more components to perform a reconstitution process. U.S. Pat. No. 6,793,646 to Giambattista et al. shows a device which allows for automated reconstitution. Specifically, to activate the device and effect reconstitution of the dry drug, the user manually causes certain components to move relative to one another axially to obtain reconstitution of a medication. The device of U.S. Pat. No. 6,793,646, however, is a single dose device which is disposable, not reusable. In addition, the device has limited variation in deliverable dosage amounts, based on a fixed arrangement of parts.
Certain drugs, once reconstituted, may have a shelf-life of several days or months. For example, human growth hormone (HGH) may have a shelf-life of up to thirty (30) days once reconstituted. For such drugs, it may be desirable to have a device which enables the user to administer repeated dosing of varying volumes of reconstituted drugs or medicaments, thus allowing for multiple doses to be administered over time.